System for measuring a multiphase flow

ABSTRACT

System for measuring a multiphase flow ( 109 ) and the flow velocity comprises: multiple wavelength source ( 101 ); multiplexer ( 103 ); first fibre optic probe ( 107 ) for transmitting optical signals into the multiphase flow and collecting reflected signals; second fibre optic probe ( 111 ) for collecting transmitted signals passing through the multiphase flow; optical circulators ( 105, 113 ) interconnected with the probes ( 107,111 ) for bidirectional transmission of the signals; a filtering device ( 114 ) such as a fibre Bragg grating for filtering the signals; wherein the collected reflected and transmitted signals are used to develop an image representation of the multiphase flow data, for example, via an image processing system ( 125 ). A reference signal may also be transmitted directly from the multiplexer ( 103 ) to the image processing system ( 125 ).

FIELD OF THE INVENTION

The present invention relates to a system for measuring a multiphaseflow data.

BACKGROUND OF THE INVENTION

Multiphase flows in oil and gas processing are measured typically forobtaining information on phase fraction and flow rate. To obtain suchinformation, flowmeters are used to detect and measure multiphase flowspassing through pipes. Different flowmeters incorporate different kindsof sensors or probes for detecting and measuring purposes.

Information on phase faction and phase velocities of a multiphase flowis crucial to well management and optimization of oil & gas productionand developments. It is a challenging task to provide accuratemeasurements of different flow conditions in upstream operations of oiland gas processing. In light of this, flowmeters with sensors and probesthat can provide reliable and accurate information are needed.

In order to provide reliable and accurate information during measurementof a multiphase flow, the present invention provides a measurementsystem using sensitive and reliable sensors so that the system cansubstantially produce accurate measurement of the multiphase flow.

SUMMARY OF THE INVENTION

In the context of this specification, the term multiphase flow refers toany fluid flow consisting of more than one phase or component.Multiphase flows can be classified according to the state of thedifferent phases or components and therefore refer to gas/solid flows,or liquid/solid flows, or gas/particle flows or bubbly flows and so on.

According to a first embodiment of the present invention, a system formeasuring a multiphase flow data using fibre optic sensors or probes isprovided. Fibre optic devices such as cables are used for transmittingand detecting optical signals to and from the multiphase flowrespectively. The operation of the system will be based on opticalreflection and absorption of the multiphase flow.

The sensors or probes will transmit optical signals with differentwavelengths from a light source. The signals will be absorbed,diffracted and/or reflected by different phases of the multiphase flow.The amount of lights that are being absorbed, diffracted and/orreflected depend on optical properties of the phases.

The emerging lights coming from the multiphase flow i.e. fromabsorption, diffraction and/or reflection bears information about thephases. The intensity of the lights will be measured and translated intouseful information. For instance, the information includes thedistribution of phases contained in the multiphase flow.

An optical multiplexing device, for example, an array waveguide grating(AWG) device is used to multiplex the light source so that the fibreoptics carry and transmit different optical wavelengths to themultiphase flow. The number of the sensors or probes can be increased sothat more information about the phases can be detected and measured toimprove the accuracy of the measurement system.

It is an object of the present invention to provide a system formeasuring a multiphase flow data using fibre optic probes that issuitable for producing information regarding the phase fraction andphase velocities of a multiphase flow.

BRIEF DESCRIPTION OF THE INVENTION

The present invention will now be described by way of example, withreference to the accompanying drawings; in which:

FIG. 1 shows a diagram of a system for measuring a multiphase flowaccording to a first embodiment of the present invention;

FIG. 2 shows a diagram of a system for measuring a multiphase flowaccording to a second embodiment of the present invention;

FIG. 3 shows an arrangement of the system for measuring phase velocity;

DETAILED DESCRIPTION OF THE PRESENT INVENTION

According to a first embodiment of the present invention, a system formeasuring a multiphase flow using fibre optic sensors is provided. Thesystem comprises a plurality of fibre optics sensors for transmittingand collecting optical signals to and from the multiphase flowrespectively, a multiplexing device for multiplexing optical source intooptical signals with different wavelengths, optical circulators forbi-directional transmission of the signals, a filtering device forfiltering signals, and an image processing system for processing thecollected signals. The processing system includes photodiodes forconverting optical signals into electrical signals. The signals will beprocessed to generate an image representation of the multiphase flowdata.

According to the first embodiment, a plurality of fibre optic sensorsare arranged around a pipe or tube to detect and measure the multiphaseflow that passes through the tube. Preferably the fibre optic sensorsare arranged normal to the tube surface. The sensors are arranged at oneend to aligned with and to face the corresponding sensors at the otherend which is used to collect the transmitted optical signals. In thisway, the multiphase flow will flow between the sensors.

The optical source is also referred to as a broadband source. Theoptical source is produced by a spontaneous emission of an amplifiedspontaneous emission (ASE) device. Preferably, straight-tipped fibreoptics are used and the multiplexing device is an arrayed waveguidegrating (AWG) device which multiplexes the optical source and allowsmultiple wavelengths to be transmitted via individual fibre opticcables.

The optical circulator used in the system is a three-port device thatallows the optical signals to travel in only one direction—from port 1to port 2, then from port 2 to port 3.

FIG. 1 shows a diagram of the first embodiment. The diagram onlyillustrates a single fibre optic connection in the system. As shown inFIG. 1, the system 100 comprises an optical source 101, a multiplexingdevice 103, a first optical circulator 105, a first collimator 107 forcollimating and transmitting optical signal, a second collimator 111 forreceiving optical signal from the first collimator 107, a filteringdevice 114 and a second optical circulator 113.

The optical source 101 is connected to the multiplexing device 103wherein the multiplexing device 103 is connected to the first opticalcirculator 105 at first port 1 wherein the first optical circulator 105is connected to the probe via the first collimator 107 via second port 2of the first optical circulator. Preferably, the first collimator 107 isarranged normal to a pipe or tube 109.

The third port 3 of the first optical circulator 105 is connected to afibre optic cable (indicated by numeral 117) that allows reflectedoptical signals from the multiphase flow inside the pipe or tube 109 tobe transmitted to the image processing system 125 via photodiode 119.

A second collimator 111 of a fibre optic sensor is provided at the otherside of the tube 109 which is placed normal to the tube 109 and parallelto the first collimator 107. In the system, the collimators are used toproduce collimated optical signals that have parallel wave-fronts. Thecollimated signals will reduce power loss and noises in the system.

The second collimator 111 is connected to a second optical circulator113 via the first port 1. The second optical circulator 113 is connectedto a filtering device 114 via second port 2. A corresponding photodiode115 is connected to the second optical circulator 113 via third port 3.

In operation, when the optical signals are transmitted from the firstcollimator 107 to a multiphase flow which flows in the pipe 109, aportion of the signals will be reflected from the multiphase flow andanother portion of the signals will be absorbed and passed through themultiphase flow. The passed through signals will be collected by thesecond collimator 111. The reflected signals will be directed to animage processing system 125 via third port 3 of the first opticalcirculator 105. The system includes photodiodes which will convert theoptical signals into electrical signals. As shown, the third port 3 isconnected to a corresponding photodiode 119. The photodiodes 115 and 119will convert the optical signals into electrical signals for imageprocessing by the image processing systems 125.

The reflected signals from the multiphase flow provide useful dataaround the circumference of the pipe 109 whereas the optical signalswhich pass through the multiphase flow provide data across the flow i.e.cross section or plane information of the flow.

Preferably, the filtering device 114 is a fibre Bragg grating (FBG)device that will filter the signals collected by the correspondingprobes. The useful optical signals will directed to the image processingsystem 125 and be converted into lo electrical signals via photodiodes.The electrical signals will be further processed by a computer for imagereconstruction or tomography. The tomography image produced from thesystem will provide, for example, intensity distributions of phasescontained in a multiphase flow.

According to a second embodiment of the present invention, a system formeasuring a multiphase flow using fibre, optic probes comprising aplurality of fibre optics for transmitting and collecting opticalsignals to and from the multiphase flow respectively, a multiplexingdevice for multiplexing optical source into optical signals withdifferent wavelengths, optical circulators for bi-directionaltransmission of signals, a filtering device for filtering the signals,photodiodes for converting optical signals into electrical signals, andan image processing system for processing the collected signals. Thesystem further comprises an optical amplifier for amplifying the opticalsignals, and an optical splitter for splitting the amplified opticalsignals.

FIG. 2 shows a diagram of the second embodiment. As shown in FIG. 2,optical signals from the AWG device 103 will be amplified by an opticalamplifier 201. The amplified signals will be then split by an opticalsplitter 203 into two portions of signals which are transmission signalsand reference signals. A large portion, for example 99% of the amplifiedsignals is split into the transmission signals and a small portion of 1%is split into the reference signals. The reference signals indicated bynumeral 205 will be directed to the image processing system 125 via acorresponding photodiode 207 which in turn converting the signals intoelectrical signals for reference data of the system. The transmissionsignals will be directed to the first optical circulator 105. The firstoptical circulator 105 is connected to fibre optic probe via the firstcollimator 107. From this point forward the system of the secondembodiment is arranged as depicted in FIG. 1.

The system either the first or second embodiment can be arranged at twodifferent locations along the pipe 109 for measuring velocity of themultiphase flow. As shown in FIG. 3, two systems are distance apart fromone another at location A and location B. For instance, time taken for amultiphase flow to travel from A to B will provide information onvelocity or flow rate.

The system according to present invention can be used as independentflowmeter or be incorporated to other flowmeter as an additionalmeasuring system.

1. A system for measuring a multiphase flow comprising: a multiplexingdevice for multiplexing an optical source into optical signals withdifferent wavelengths for transmission into the multiphase flow; atleast a first fiber optic probe for transmitting the optical signalsinto the multiphase flow and collecting reflected signals; at least asecond fiber optic probe for collecting the optical signals passingthrough the multiphase flow; optical circulators with a plurality ofports interconnected with the probes for bi-directional transmission ofthe signals; and a filtering device for filtering the signals; whereinthe collected optical signals are used to develop an imagerepresentation of the multiphase flow. 2-25. (canceled)
 26. The systemfor measuring a multiphase flow according to claim 1, wherein the imagerepresentation of the multiphase flow is developed by an imageprocessing system.
 27. The system for measuring a multiphase flowaccording to claim 26, wherein the image processing system includesphotodiodes for converting the optical signals into electrical signals.28. The system for measuring a multiphase flow according to claim 1,wherein the fiber optic probes are arranged around a pipe where themultiphase flow passes through.
 29. The system for measuring amultiphase flow according to claim 1, wherein the first fiber opticprobe is arranged to align with and face the second fiber optic probe.30. The system for measuring a multiphase flow according to claim 1,wherein each of the fiber optic probes includes a collimator positionednormal to a pipe surface.
 31. The system for measuring a multiphase flowaccording to claim 1, further comprising an optical source directed tothe multiplexing device.
 32. The system for measuring a multiphase flowaccording to claim 1, wherein the multiplexing device is connected to afirst optical circulator via a first port.
 33. The system for measuringa multiphase flow according to claim 32, wherein the first opticalcirculator is connected to the first fiber optic probe via a secondport.
 34. The system for measuring a multiphase flow according to claim33, wherein the first optical circulator is connected to an imageprocessing system via a third port for directing reflected signals to animage processing system.
 35. The system for measuring a multiphase flowaccording to claim 32, wherein the second fiber optic probe is connectedto a second optical circulator via a first port for directing opticalsignals to the filtering device at a second port.
 36. The system formeasuring a multiphase flow according to claim 35, wherein the filteredsignals from the filtering device are directed to an image processingsystem via a third port of the second optical circulator.
 37. The systemfor measuring a multiphase flow data according to claim 1, wherein thesystem further comprises at least an optical amplifier for amplifyingthe optical signals and at least an optical splitter for splitting theamplified optical signals into multiple portions of signals.
 38. Thesystem for measuring a multiphase flow according to claim 37, whereinthe optical amplifier is connected to the optical splitter.
 39. Thesystem for measuring a multiphase flow according to claim 37, furthercomprising an optical source directed to the multiplexing device. 40.The system for measuring a multiphase flow according to claim 37,wherein the multiplexing device is connected to the optical amplifier.41. The system for measuring a multiphase flow according to claim 37,wherein the optical splitter is connected to a first optical circulatorvia a first port for directing a first portion of the signals.
 42. Thesystem for measuring a multiphase flow according to claim 41, whereinthe optical splitter is connected to an image processing system fordirecting a second portion of the signals.
 43. The system for measuringa multiphase flow, according to claim 41 wherein a first opticalcirculator is connected to the first fibre optic probe via a secondport.
 44. The system for measuring a multiphase flow according to claim43, wherein the first optical circulator is connected to the imageprocessing system via a third port.
 45. The system for measuring amultiphase flow according to claim 42 wherein the first portion of thesignals is for transmission to the multiphase flow and the secondportion is for reference of the image processing system.
 46. The systemfor measuring a multiphase flow according to claim 1, wherein themultiplexing device is an arrayed waveguide grating device.
 47. Thesystem for measuring a multiphase flow according to claim 1, wherein thefiltering device is a fibre Bragg grating device.
 48. A system formeasuring a multiphase flow according to claim 31, wherein the opticalsource is an amplified spontaneous emission broadband light.
 49. Asystem for measuring a multiphase flow comprising, at least two systemsaccording to claim 1, wherein the systems are placed at two differentlocations along a pipe for measuring velocity of a flow through thepipe.